General

Why doesnt Mr. Fantastic use his powers like Luffy does?

I was watching the movie,and I had started to wonder about it. He can already stretch and move his body just like Luffy, so I would think it would make sense
that he would use his powers like him, instead of picking up objects and throwing them. Is it a copyright problem,because they cant "steal" Luffy's moves and style of fighting?
what do you guys think about it?